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- 일시: 08.02(금) 11:00~, 공대6호관 319호실

- 연사: Dr. Sunghyun Kim, Department of Materials, Imperial College London, UK

- 주제: Theoretical Maximum Photovoltaic Efficiency of Real Materials: Kesterite Solar Cells

The theoretical maximum efficiency of a solar cell such as Shockley-Queisser limit has mainly focused on the radiative recombination as the limiting factor. However, in practical solar cells, the nonradiative recombination is unavoidable due to the formation of native point defects and often the dominant recombination mechanism [1].

We will predict the theoretical maximum efficiency of kesterite solar cells (Cu_2Zn(Ge,Sn)(S,Se)_4), taking into account both radiative recombination and non-radiative carrier recombination mediated by the native point defects. We calculate the thermal equilibrium concentrations of native defects and their capture cross-sections. we find that the sulfur vacancy (V_S), sulfur vacancy-donor complex and Sn antisites (Sn_Zn) produce deep levels and large capture cross-sections resulting in the low open-circuit voltage and the low solar-to-electricity conversion efficiency [2, 3]. The predicted upper limit is compared to the current generation of best performing kesterite solar cells. We suggest that the codoping and alloying may improve the efficiency of kesterite solar cells.

[1] Point defect engineering in thin-film solar cell. Nat. Rev. Mat. 3, 194 (2018)

[2] Identification of Killer Defects in Kesterite Thin-Film Solar Cells. ACS Energy Lett. 3, 496 (2018)

[3] Lone-pair effect on carrier capture in Cu2ZnSnS4 solar cells. J. Mater. Chem. A 7, 2686 (2019)